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+As I was looking for a system to store documents at $work, Riak was
+pointed to me by one of my coworkers. I'm looking for a solution of this
+type to store various types of documents, from HTML pages to json. I
+need a system that is distributed, faul tolerant, and that works with
+Perl.
+
+So Riak is a document based database, it's key value, no sql, REST, and
+in Erlang. You can read more about it here or watch an introduction
+here. Like <ahref="http://couchdb.apache.org/">CouchDB, Riak provides a
+REST interface, so you don't have to write any Erlang code.
+
+One of the nice things with Riak it's that it let you defined the N, R
+and W value for each operation. This values are:
+
+-  N: the number of replicas of each value to store
+-  R: the number of replicas required to perform a read operation
+-  W: the number of replicas needed for a write operation
+
+Riak comes with library for python ruby PHP and even javascript, but not
+for Perl. As all these libraries are just communicating with Riak via
+the REST interface, I've started to write one using AnyEvent::HTTP, and
+also a backend for KiokuDB.
+
+** Installing and using Riak
+
+If you interested in Riak, you can install it easily. First, you will
+need the Erlang VM. On debian, a simple
+
+#+BEGIN_EXAMPLE
+    % sudo aptitude install erlang
+#+END_EXAMPLE
+
+install everything you need. Next step is to install Riak:
+
+#+BEGIN_EXAMPLE
+    % wget http://hg.basho.com/riak/get/riak-0.6.2.tar.gz
+    % tar xzf riak-0.6.2.tar.gz
+    % cd riak
+    % make
+    % export RIAK=`pwd`
+#+END_EXAMPLE
+
+Now, you can start to use it with
+
+#+BEGIN_EXAMPLE
+    % ./start-fresh config/riak-demo.erlenv
+#+END_EXAMPLE
+
+or if you want to test it in cluster mode, you can write a configuration
+like this:
+
+#+BEGIN_EXAMPLE
+        {cluster_name, "default"}.
+        {ring_state_dir, "priv/ringstate"}.
+        {ring_creation_size, 16}.
+        {gossip_interval, 60000}.
+        {storage_backend, riak_fs_backend}.
+        {riak_fs_backend_root, "/opt/data/riak/"}.
+        {riak_cookie, riak_demo_cookie}.
+        {riak_heart_command, "(cd $RIAK; ./start-restart.sh $RIAK/config/riak-demo.erlenv)"}.
+        {riak_nodename, riakdemo}.
+        {riak_hostname, "192.168.0.11"}.
+        {riak_web_ip, "192.168.0.11"}.
+        {riak_web_port, 8098}.
+        {jiak_name, "jiak"}.
+        {riak_web_logdir, "/tmp/riak_log"}.
+#+END_EXAMPLE
+
+Copy this config on a second server, edit it to replace the
+riak\_hostname and riak\_nodename. On the first server, start it like
+show previously, then on the second, with
+
+#+BEGIN_EXAMPLE
+    % ./start-join.sh config/riak-demo.erlenv 192.168.0.11
+#+END_EXAMPLE
+
+where the IP address it the address of the first node in your cluster.
+
+Let's check if everything works:
+
+#+BEGIN_EXAMPLE
+    % curl -X PUT -H "Content-type: application/json" \
+        http://192.168.0.11:8098/jiak/blog/lumberjaph/ \
+        -d "{\"bucket\":\"blog\",\"key\":\"lumberjaph\",\"object\":{\"title\":\"I'm a lumberjaph, and I'm ok\"},\"links\":[]}"
+
+    % curl -i http://192.168.0.11:8098/jiak/blog/lumberjaph/
+#+END_EXAMPLE
+
+will output (with the HTTP blabla)
+
+#+BEGIN_EXAMPLE
+        {"object":{"title":"I'm a lumberjaph, and I'm ok"},"vclock":"a85hYGBgzGDKBVIsbGubKzKYEhnzWBlCTs08wpcFAA==","lastmod":"Sun, 13 Dec 2009 20:28:04 GMT","vtag":"5YSzQ7sEdI3lABkEUFcgXy","bucket":"blog","key":"lumberjaph","links":[]}
+#+END_EXAMPLE
+
+** Using Riak with Perl and KiokuDB
+
+I need to store various things in Riak: html pages, json data, and
+objects using KiokuDB. I've started to write a client for Riak with
+AnyEvent, so I can do simple operations at the moment, (listing
+information about a bucket, defining a new bucket with a specific
+schema, storing, retriving and deleting documents). To create a client,
+you need to
+
+#+BEGIN_SRC perl
+    my $client = AnyEvent::Riak->new(
+        host => 'http://127.0.0.1:8098',
+        path => 'jiak',
+    );
+#+END_SRC
+
+As Riak exposes to you it's N, R, and W value, you can also set them in
+creation the client:
+
+#+BEGIN_SRC perl
+    my $client = AnyEvent::Riak->new(
+        host => 'http://127.0.0.1:8098',
+        path => 'jiak',
+        r    => 2,
+        w    => 2,
+        dw   => 2,
+    );
+#+END_SRC
+
+where:
+
+-  the W and DW values define that the request returns as soon as at
+   least W nodes have received the request, and at least DW nodes have
+   stored it in their storage backend.
+-  with the R value, the request returns as soon as R nodes have
+   responded with a value or an error. You can also set this values when
+   calling fetch, store and delete. By default, the value is set to 2.
+
+So, if you wan to store a value, retrieve it, then delete it, you can
+do:
+
+#+BEGIN_SRC perl
+    my $store =
+        $client->store({bucket => 'foo', key => 'bar', object => {baz => 1},})
+        ->recv;
+    my $fetch = $client->fetch('foo', 'bar')->recv;
+    my $delete = $client->delete('foo', 'bar')->recv;
+#+END_SRC
+
+If there is an error, the croak method from AnyEvent is used, so you may
+prefer to do this:
+
+#+BEGIN_SRC perl
+    use Try::Tiny;
+    try {
+        my $fetch = $client->fetch('foo', 'baz')->recv;
+    }
+    catch {
+        my $err = decode_json $_;
+        say "error: code => " . $err->[0] . " reason => " . $err->[1];
+    };
+#+END_SRC
+
+The error contains an array, with the first value the HTTP code, and the
+second value the reason of the error given by Riak.
+
+At the moment, the KiokuDB backend is not complete, but if you want to
+start to play with is, all you need to do is:
+
+#+BEGIN_SRC perl
+    my $dir = KiokuDB->new(
+        backend => KiokuDB::Backend::Riak->new(
+            db => AnyEvent::Riak->new(
+                host => 'http://localhost:8098',
+                path => 'jiak',
+            ),
+            bucket => 'kiokudb',
+        ),
+    );
+
+    $dir->txn_do(sub { $dir->insert($key => $object) });
+#+END_SRC